LM5156: Is there any method the output voltage based on different input voltage?

Hi all, I am new to use this LM5156, since I want to make a non isolated booster circuit using LM5156, input voltage is 15~21V, and output we desired it may change from 24V to 29V due to different input voltage.

I was check that the output voltage is modified by FB pin with voltage divider from output voltage, so I try to change the FB pin pick voltage from output to input. However, the result of output voltage is swing very high (sometime change to >60V suddenly).

May I know is this possible to using input voltage to reference the output voltage? is there any additional circuit I need to build? thanks!

Johnsin Tao：

HI

    可以尝试在输入电压和反馈FB之间增加一个电阻，如果输入电压变化，就会调节到反馈。

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Simon Poon：

你好 Johnsin, 請問你的意思是這樣連接嗎?我會試試看的,謝謝!

 

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Johnsin Tao：

Hi

    是的，但是原有的反馈电阻也是需要的。

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Simon Poon：

Hi, 你指原有的反饋電阻是指Vout 接電阻到FB那一顆嗎(圖中的Rfbt)?那會跟輸入到反饋的電阻導通了嗎?

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Johnsin Tao：

HI

    是的，将输入的变化引导到输出。